The present invention relates generally to the art of electromechanical machines having a rotating shaft, such as generators and electric motors. More particularly, the invention relates to an arrangement for shielding the shaft of an electromechanical machine to lessen the generation of errant shaft currents.
The shaft of an electromechanical machine is often supported by bearing assemblies maintained in position by the machine housing. In one known construction, each bearing assembly is supported by a portion of the housing known as the "end bell." As its name implies, the end bell is located at one axial end of the housing, and defines a hole through which the rotatable shaft freely extends. The machine may be constructed to either allow or prevent slight axial movement of the bearing assembly, depending upon the exigencies of a particular application.
Operation of the machine will often cause various currents to be produced in the rotating shaft. Seeking ground, the currents may flow through the bearing assembly into the machine's housing. Flow of current through the bearing assembly in this manner may give rise to more frequent maintenance requirements or other problems in the operation of the machine. For example, the currents can arc to the bearing elements, causing "pits" or other undesirable effects.